spritzer

I placed the filter cap before the divider and used 270K to ground but it really doesn't matter.

It is already a divider so it's better to use the regulated B+.

You only need to alter the bias supply for the amp to work with normal bias phones. See here: That is the bias supply for the normal bias on the right hand side panel of the amp, just behind the front panel. Just a voltage divider off the B+ with a small filter cap, two resistors to form the divider and a 4M7 ballast resistor.

If the sound comes and goes then it is probably the cable, not the drivers. That's exactly how a broken bias wire works... Edit: Normal bias has separate bias for each driver unlike the pro stuff.

Yeah, schematics are for the weak.

...also depends on the transformers used.

Fucking hope not as they seem to like me a lot. I always get extra discounts and the shipping is silly cheap. Might also be because a I buy a lot of boxes from them... a lot...

I can't log into their new site so some teething problems.

It's ok to just do the calculations... 625VDC*.707= 441VAC. Edit: The 450V version doesn't need this much as it has a voltage doubler which generates the bias voltage which is then regulated down to 580VDC

This is for the PSU, not the amp boards. There you need 1kV as it's for the doubler. For the amp side, anything above the rails will work.

485V is very much on the high side. Your pass transistors will get very, very warm indeed. 450V would be the max for a +/-500V amp. Up the current a bit instead.

It should be ok but one never knows until the switch is flipped for the first time.

No, not really. It should work but a trace might be deleted by mistake (that has happened) and then all hell breaks loose. Just fire one up and see if it works.

Different layout. Use the former as it is more recent.

Yup, they were bought for projects which haven't materialized yet.

Plenty of 100nf/1000V caps to be found. This one should work just fine: http://www2.mouser.com/ProductDetail/Kemet/PHE426PB6100JR06/?qs=sGAEpiMZZMv1cc3ydrPrF85GIl804cbNm959%252bOSJvME%3d Cheap too. You can use that PSU but you could have problems. Plus nobody has ever built that PSU there might be massive problems. I just found out over the weekend that the layout software we use has a brand new way of fucking us over with no warning. Stick with the BHSE unit.

I use mine as paperweights...

The spacing is 15mm so go from there.

With +/-400V supplies it is far higher.

Not counting the few thousand units in stock at Mouser?

So... when do you want me there?

Yup and be warned, this is very fiddly. That's why I don't touch the Sigma's any more.

+/-20V doesn't matter the slightest bit.

This is common for the circuit and poses no harm for the headphones.

The 007A/Mk2 is an alternative too, different but also good. That means a more balanced budget.